1. Field of the Invention
The present invention relates to glass nozzle arrays and the method of producing them, and more particularly, to glass nozzle arrays of the type usable in an ink jet printing apparatus as orifices in an orifice plate or holes in a charge plate assembly.
2. Prior Art
Ink jet printing apparatus of the type in which the present invention is intended to be utilized, produce a plurality of uniform drops aligned parallel to one another and perpendicular to the movement of paper or other material upon which printing is to be effected. The printing is produced by using a reservoir of printing fluid (herein referred to as ink, but which can have varying compositions as is well known in the art) with a plurality of parallel aligned orifices at the bottom of the reservoir. through which the fluid is ejected or permitted to flow at a predetermined rate and in such a manner as to produce drops of fluid at the ends of filaments of the ink which pass through the orifice. These drops are then selectively charged or not charged as they pass through holes in a charge plate and are subsequently caught in a catcher or deposited on the material which is being printed.
Two somewhat distinct methods have been developed for generating the filaments and uniform drops which stem from the orifices. The first is the use of a vibrating orifice plate such as that disclosed in U.S. Pat. No. 3,739,393, in which a mechanical stimulator causes uniform vibration through a relatively thin orifice plate so that movement of the orifice plate causes droplets to be uniformly produced at the ends of the filaments extending from the orifices, in a well known manner. The second method is in the utilization of a vibrating plate above the liquid reservoir in contact with the liquid and parallel to a relatively thick and rigid orifice plate so that the ink is pushed through the orifices under pressure created by uniform vibration of the vibrating plate acting on the liquid. Such a method is disclosed in U.S. Pat. No. 3,900,162.
The present invention is directed more particularly to the latter type of ink jet printing apparatus in which the orifice plate is intended to be relatively rigid.
Economical methods of forming the orifices in the orifice plate or holes in the charge plate are difficult to find since the nature of the system requires the use of extremely small diameter holes in these plates. For example, the orifices in the orifice plate are generally in the range of 0.0005 to 0.0015 inch in diameter and the holes in the charge plate are generally in the range of 5 to 10 mils in diameter. In the past, this has required very expensive, time consuming and exotic methods of manufacturing orifice plates and charge plates having uniformly spaced and uniform diameter orifices ahd holes, respectively.
Exemplary systems include those such as disclosed in "IBM Technical Disclosure Bulletin" Volume 13, No. 11, page 4146, dated May 1976, in which an aluminum oxide block of material is compressed or formed about a plurality of parallel spaced wires and the wires are then subsequently etched out of the material to produce the desired diameter holes or orifices, and such a system as is disclosed in "IBM Technical Disclosure Bulletin" Volume 17, No. 11, page 3269, dated April 1975, in which a plurality of relatively large outside diameter glass tubes are ground to rectangular configuration, then drawn to reduce the inside diameter of the tubes and subsequently packaged in a bundle and heated to effect bonding between blocks by melting the glass. Such methods are very expensive and difficult to perform.
Another example of an attempt to produce such a construction is given in German Pat. No. 2,555,295 in which a method of forming a single nozzle from the glass tube is disclosed, in which a single glass tube is placed in a ceramic housing, the housing is then filled with glass and heated to cause bonding of the assembly with subsequent slicing to produce the wafer-thin nozzle portion. However, this is only directed to production of a single nozzle and not multiple aligned nozzles as is the present invention.
A further prior art process is disclosed in U.S. Pat. No. 2,996,419, in which a plurality of glass tubes are merely stacked parallel in a container and then the container is filled with an epoxy and metal mixture which is then cured. However, this system would not be appropriate for producing parallel aligned glass nozzle arrays of the type to which the present invention is directed.